SAN DIEGO — San Diego Chargers linebacker Stephen Cooper is vowing never to use supplements again, after returning from a four-game suspension imposed by the NFL for testing positive for a banned stimulant.

"Honestly, I'm not touching nothing," said Cooper, who took responsibility for his mistake.

Cooper led the Chargers with 179 tackles last season, when they made it to the AFC championship game. He had to watch as the Chargers lost their first two games this season before reaching .500 with wins over the New York Jets and Oakland Raiders.

Cooper says he'll have to compete to win back his starting job. The Chargers play at Miami on Sunday.